The present study seeks to continue into preadolescence and adolescence a longitudinal study of personality and cognitive development. The subject sample initially was studied at the age of three years, then at four, at five and at seven years. Extensive experimental and other data available from each of these time periods on these children and on their parents. Extensive additional experimental and other data will be collected during the adolescent period. The theoretical focus of the study is on the broad conceptual variables, ego control and ego resiliency. The research analyses are oriented toward understanding the antecedents of ego control and ego resiliency in both boys and girls, exploring the reciprocal implications of ego control and ego resiliency for cognitive development, and tracing the ramifications of ego control and ego resiliency in the wider and social world of adolescence.